How to make slime for Halloween

Slime is a non-Newtonian fluid: something that ignores Newton’s law of viscosity, flowing under certain conditions but stiffening when compressed quickly. The most famous non-Newtonian fluid is custard, but in the 1970s toy manufacturers latched on to serendipitous discoveries of non-Newtonian polymers made by the chemical industry. One such substance was marketed as ‘Slime’ by Mattel which, thanks to an engaging TV advert and the popularity of movies such as Ghostbusters, became a household name.